Ask the Sailmaker
Mary, got some ideas for you. First, (Plan A) look at the sail bag for the name of the sailmaker. Standardly a loft will have the sailmaker, year, and sail type on the bag (at least North and Lidgard/Seattle does). Another place to look is on the sail, maybe near the tack if it's a jib and maybe in the lower middle of the sail if it's a spinnaker. Go on-line and find the sailmaker and maybe the nearest loft and start communicating to them what you have. The loft keeps the records, hopefully on computer, and hopefully they can search by owners name (previous owner) or boat name. Once they find the record, which should take only a few minutes if it's on a computer, they can tell you everything about the sail.Plan B, if you reach a dead-end on the above, would be to talk to any loft you can find, if they're cooperative, and see if they can help you figure out what kind of sail it is. Depending on who you talk to, time of day, if they're "booked" or not, you can get some free help. At this point they may ask for length measurements of the three sides of the sail so be prepared to take out the tape measure.You said it looks like a "rainbow"; if the seams are curved instead of triangles or straight lines it sounds like a UK "tape drive" sail.In order to learn how to fly the sail one needs to know what it is so it's smart that you're digging into finding out what you have. Good luck in your research.